Dragon Ball Super's new movie should make Janemba a part of the official series' canon. One of the most exciting aspects of Dragon Ball Super: Broly was that it officially introduced the non-canon movie villain Broly to the main series. With a new story and character design from series creator Akira Toriyama, Broly was able to fit right into the current Dragon Ball Super timeline. Toei Animation is releasing a new Dragon Ball Super movie in 2022, and they confirmed that production began on it before the release of Dragon Ball Super: Broly. Maybe it was with the intention of introducing another villain into the canon?
There are lots of potential classic Dragon Ball movie villains that would do well with a major makeover and new origin, but not all of them would fit into Goku and Vegeta's now godly levels of power. If the new movie takes place in the current canon of the series (and accounting for the advancements Goku and Vegeta have seen in the Galactic Patrol Prisoner and Granolah the Survivor arcs from the manga), Janemba might be the only villain who could fit this new movie role.
There is potential for new movie's villain to be an original creation entirely, but assuming that's not the case, any new foe is going to need to be able to keep up with the current Goku and Vegeta. Even if it's just factoring in Dragon Ball Super: Broly power levels, the list of Dragon Ball movie villains shrinks dramatically when figuring out which of the villains could theoretically keep or be powered up to the level of godhood.
Making things even more complicated is that a movie villain's story needs to be resolved by the end of it, so you need a character that won't take a lot of explanation to make work and be believable enough to quickly gain god level strength. Goku and Vegeta have yet to fight a demon during the events of Dragon Ball Super thus far, and with Gods and Angels already on the table, take it to the next step with demons.
Bring Janemba in as a powerful reflection of the gods, or take it one step further and have the villain be a fallen Angel or God that somehow evaded erasure. Akira Toriyama would most definitely think of a cool and easy way to bring in demons fully to this multiverse, and the story implications it could have for the future of the franchise would amp up the story's scale without needing to completely reinvent the wheel.
Janemba wouldn't need to be around for a long time to leave an impact, and Toei Animation could look towards the response to Janemba's debut in the first place as a strong example of this. Like Broly did before, Janemba would greatly expand the kinds of stories that Dragon Ball Super could explore in the manga. It could also make for an easy one-off kind of battle that could fit in at any point of the time line now being fleshed out in the manga release.
Any movie that branches off next is going to need to incorporate Ultra Instinct Goku in some way (regardless of whether or not the manga's stories are referenced), so it's going to need a foe to withstand it. Janemba is just that. He comes with a whole new faction of foes, a new part of the multiverse, a new dimension making for a great final climactic set piece, and a power level to match. Plus, Toriyama would give us a whole new design!
What do you think? Would Janemba be a great fit for the Dragon Ball Super canon? Would you like to see the foe come back, or another classic villain? Let us know your thoughts in the comments or you can even reach out to me directly about all things animated and other cool stuff @Valdezology on Twitter!